Automatic alignment of a contrast enhancement system

ABSTRACT

An apparatus and method for insuring the proper alignment of a detected vein pattern and a projected vein pattern are disclosed. The apparatus enhances the visual appearance of veins so that an error that can lead to improper patient care or injury can be avoided.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/665,504, filed Aug. 1, 2017, which is a continuation of U.S.application Ser. No. 15/226,027, filed Aug. 2, 2016, which is acontinuation of U.S. application Ser. No. 14/196,172, filed Mar. 4,2014, now issued as U.S. Pat. No. 9,430,819, which is a continuation ofU.S. application Ser. No. 12/215,713, filed Jun. 27, 2008, now issued asU.S. Pat. No. 8,730,321, which claims priority on U.S. ProvisionalApplication Ser. No. 60/937,618, filed Jun. 28, 2007, all disclosures ofwhich are incorporated herein by reference.

SUMMARY OF THE INVENTION

An apparatus and method for insuring the proper alignment of a detectedvein pattern and a projected vein pattern in a apparatus that enhancesthe visual appearance of veins so that an error that can lead toimproper patient care or injury can be avoided.

BACKGROUND OF THE INVENTION

It is known in the art to use an apparatus to enhance the visualappearance of the veins and arteries in a patient to facilitateinsertion of needles into those veins and arteries as well as othermedical practices that require the identification of vein and arterylocations. Such a system is described in U.S. Pat. Nos. 5,969,754 and6,556,858 incorporated herein by reference as well as publicationentitled “The Clinical Evaluation of Vein Contrast Enhancement”.Luminetx is currently marketing such a device under the name “VeinviewerImaging System” and information related thereto is available on theirwebsite, which is incorporated herein by reference.

The Luminetx Vein Contrast Enhancer (hereinafter referred to as LVCE)utilizes a light source for flooding the region to be enhanced with nearinfrared light generated by an array of LEDs. A CCD imager is then usedto capture an image of the infrared light reflected off the patient. Theresulting captured image is then digitally enhanced and then projectedby a visible light projector onto the patient in a position that must beclosely aligned with position of the captured image. The practitioneruses this projected image to determine the position in which to insert aneedle. Should the image be misaligned, the patient can be injured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a vein contrast enhancer.

FIG. 2 is a representation of a patient's arm.

FIG. 3 shows an embodiment of a laser contrast enhancer.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a typical embodiment of a vein contrast enhancer(VCE) 100 contains a camera 101 which is used to capture an image of apatient's body 105, a processing system (not shown) that enhances theimage captured by the camera to highlight the positions of veins, and aprojector 102 that shows an image of the enhanced vein pattern back ontothe patient's body 105. Since the camera and projector are physicallyseparate devices they reach the patient's body from different sourcepoints along different paths 103, 104. In some embodiments, the pathsare made coaxial within the body of the VCE, however at some point thepaths are separate since the devices (camera and projector) arephysically separate devices. Since the purpose of a VCE is to allow thepractitioner to insert a needle into the highlighted vein, it iscritically important that the projected image and the actual veinlocation be aligned. Typically this alignment is done as a separate stepin the use of the VCE. A card with a known pattern is placed with theviewing/projecting field of the VCE. This card has a florescent materialapplied to it so that when it is struck by green light, it emitsinfrared light that can be seen by the camera. This image is used toalign the VCE.

This invention describes methods for achieving this alignment withoutrequiring the operator to take a separate step.

Referring to FIG. 2, a representation of the patient's arm 201 is shownalong with several veins. A bounding box is shown around a single vein200. In FIG. 3, a schematic representation of the bounded area of thesingle vein is shown 305. Typically, the enhancement image will light upthe area around the vein and will be dark on the vein. When properlyaligned, the bright part of the image 300 will have edges that properlyalign with the edges of the vein 303, 304. As previously described, theVCE will typically have an alignment mode wherein a known pattern,typically presented on an alignment card, will be placed in front of theVCE and an alignment will be performed. This alignment can either beautomatically performed by the VCE or manually performed by theoperator. The weakness of this kind of implementation is that it relieson the expectation that the alignment will be maintained over time. Ifthe alignment should shift, patient injury can occur.

In a typical VCE, an infrared light source and a camera that issensitive only to infrared light is used to detect the vein position.Furthermore, the projected image is often green in color to insure thatthe light from the projector is ignored since the camera is sensitiveonly to light near the infrared region. This selectivity can beimplemented either with filters or with selectively sensitive cameraelements.

Referring back to FIG. 3, in a typical LCE, the camera, by design, isblind to the projected light. In our invention, the camera is by design,able to selectively see the projected light. In a preferred embodiment,a multi-color capable projector is used. As usual, green is used to fillthe area outside of the vein 300. That green projection goes to theedges of the vein position 303, 304 and the vein area itself is leftdark. A camera that is sensitive to red and infrared light is used inthis embodiment. In addition to the green fill, red lines are drawn atthe edges of the veins 303, 304. Since the camera can see these redlines, the image enhancement software can look to see if the red linesare at the proper position and if needed automatic alignment can beperformed. An alternative embodiment would be to paint a red line 306down the middle of the vein position. An alternative embodiment would beto paint some pattern of red light over a desired portion of the vein.

Typically the cameras used in an LCE are monochrome and unable todiscriminate between light of different wavelengths. Depending on thesensitivity of the camera and the brightness of the projector comparedto the infrared flood lighting provided by the LCE, various techniquescan be used to aid the camera in the detection of the red lines. Onemethod is to simply look for the brightening caused by the addition ofthe red lines to the reflected infrared light. A second method is toperiodically turn off the infrared lighting such that only ambientinfrared and the projected red are seen by the camera. This can make iteasier for the system to detect the red lines.

Although we've described the invention using red and green lights,various combinations of colors can be used. Red and infrared light areknown in the art to be useful for vein detection. Any combinations ofcolors of shorter wavelengths can be used for projection and alignmentimages as long as the camera selected is properly selected or filteredto achieve the desired discrimination between wavelengths. Furthermore,while discrimination between projection, detection and alignment signalsin the preferred embodiment has been described using differentwavelengths to separate the signals, in an embodiment with less freedomof projected color, time division can be used where the projected imageis shown most of the time and the alignment image is shown interspersedon a lower duty cycle basis. Properly implemented, the alignment imagewill be quite visible to the VCE's camera, but invisible to the operatorof the VCE.

Projectors in VCEs can be either monochrome (e.g., projecting greenonly) or multicolor (e.g., projection RGB). The advantage of amonochrome implementation is that since an array of single color LEDscan be used in place of white bulbs and a color wheel is typically foundin a multicolor projector the system can be of lower cost, generate lessheat and have higher reliability. In such an embodiment, the timedivision scheme describe above would be appropriate. In this monochromeconfiguration, an alternative embodiment would be to add a smaller arrayof a second color of LEDs (i.e., red). This alignment array can besmaller than the projection array in that it doesn't need to be visibleto the operator, just to the camera. The projection LEDs and thealignment LEDs could then be time multiplexed as previously described.

We claim:
 1. A vein imaging system comprising: a light source thatilluminates a field of view with a first wavelength of light comprisingan infrared wavelength, to create an image contrast of one or more veinsformed by differential amounts of absorption and reflection of saidfirst wavelength of light by the one or more veins and surroundingtissue in the field of view; an alignment card comprising a pattern,said pattern comprising a material that emits a second wavelength oflight when exposed to a third wavelength of light comprising a visiblewavelength; a camera configured to capture said image contrast of theone or more veins at said first wavelength of light; a projectorconfigured to receive and to project said captured image contrast ontothe field of view using said third wavelength of light; wherein saidcamera is further configured to capture said second wavelength of lightemitted by said pattern when positioned in the field of view, and tocapture said visible light at said third wavelength of light reflectedfrom said pattern, said camera further configured to distinguish saidthird wavelength of light reflected by said pattern, from said secondwavelength of light emitted by said pattern; and an image processorconfigured to align said projection of said image contrast with saidimage contrast formed by the differential absorption and reflection,using said distinction between said captured reflection of said patternat said third wavelength of light, and said captured emission from saidpattern at said second wavelength of light.
 2. The vein imaging systemaccording to claim 1 wherein said pattern comprises a fluorescentmaterial.
 3. The system according to claim 1 wherein said patterncomprises a known pattern.
 4. The vein imaging system according to claim1 wherein said third wavelength of light comprises a green wavelength oflight.
 5. The vein imaging system according to claim 4 wherein saidsecond wavelength of light comprises a red wavelength of light.
 6. Thevein imaging system according to claim 5 wherein said green wavelengthof light of said projected image contrast is projected onto the field ofview outside of the one or more veins.
 7. The vein imaging systemaccording to claim 1 wherein said visible third wavelength of light andsaid infrared first wavelength of light are alternately projected andilluminated, respectively.
 8. The vein imaging system according to claim7 wherein said visible third wavelength of light is projected at ahigher duty cycle than said illumination with said infrared wavelength.9. A vein imaging system comprising: a light source that illuminates afield of view with a first wavelength of light comprising an infraredwavelength, to create an image contrast of one or more veins formed bydifferential amounts of absorption and reflection of said firstwavelength of light by the one or more veins and surrounding tissue inthe field of view; a camera configured to capture said image contrast ofthe one or more veins at said first wavelength of light; a projectorconfigured to receive said captured image contrast and to project linesat an edge of each of the one or more veins in said captured imagecontrast with a second wavelength of light, said second wavelength oflight comprising a visible wavelength; wherein said camera is furtherconfigured to capture said projected edge lines for the one or moreveins at said second wavelength of light reflected from the field ofview, and to distinguish said captured edge lines of the one or moreveins at said second wavelength of light from the edge of each of theone or more veins in said contrasted image at said first wavelength oflight; and an image processor configured to align said projection ofsaid edge lines for each of the one or more veins with said reflectededge lines of the one or more veins.
 10. The vein imaging systemaccording to claim 9 wherein said visible second wavelength of light andsaid infrared first wavelength of light are alternately projected andilluminated.
 11. The vein imaging system according to claim 9 whereinsaid projected visible third wavelength of light is projected at ahigher duty cycle than said illumination of said infrared wavelength.12. The vein imaging system according to claim 9 wherein said visiblesecond wavelength of light comprises a green wavelength of light.